I know of one chair who sent out a letter saying the shoes left outside doors were a safety issue, especially in the event of a fire and they would be removed. It had immediate results.
Remember, you don’t have to wait for people to comply. Issue a warning then go round one night and collect the shoes and leave them in a bin where people can retrieve them.
If the shoe owners have a problem, let them take the committee to NCAT, not the other way round.